VB.NET HTTPS WEBREQUEST

Question

I have a VB.NET code that posts a text file using httpwebrequest. Once the URL was changed from http:// to https:// the code is not working anymore, and the following message is being generated: "The remote server returned an error: (407) Proxy Authentication Required."

Note that, I tried to post the file manually using POSTMAN (on google chrome) and it worked just fine without asking for proxy authentication. Why is this error message generated only when I try to post my text file using the vb.net code and how could I fix it?

Here is my code:

Imports System


Imports System.IO
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Diagnostics
Imports System.Linq
Imports System.Text
Imports System.Threading.Tasks
Imports System.Configuration
Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq
Imports System.Net
Imports System.Threading
Imports System.Security.Cryptography.X509Certificates
Imports System.Net.Security
Module Module1

Sub Main()
    Dim dateTime As String = " "
    Dim createddate As String = " "
    Dim headerbytelength() As Byte
    Dim endboundlength() As Byte
    Dim e As String = "Test.txt"
    dateTime = DateAndTime.Now.ToString()
    createddate = DateAndTime.Now.ToString("yyyyMMdd_HHmmssfff")
    Dim strRequestURL = ConfigurationManager.AppSettings("strRequestURL").ToString()
    Dim strFilename = ConfigurationManager.AppSettings("Path") + e
    Dim request As HttpWebRequest = CType(WebRequest.Create(strRequestURL), HttpWebRequest)

    request.Method = "POST"
    CType(request, HttpWebRequest).UserAgent = ".NET Framework Example Client"
    Dim response As HttpWebResponse
    Dim JSONResponse As String = ""
    Dim writer As TextWriter = New StreamWriter(ConfigurationManager.AppSettings("LogPath"), True)
    writer.WriteLine("")
    writer.WriteLine("File name: " + e + "    Date/Time: " + createddate)
    writer.WriteLine("")

    Try
        System.Threading.Thread.Sleep(ConfigurationManager.AppSettings("Delay"))
        Dim boundary As String = IO.Path.GetRandomFileName
        Dim header As New System.Text.StringBuilder()
        header.AppendLine("--" & boundary)
        header.Append("Content-Disposition: form-data; name=""file"";")
        header.AppendFormat("filename=""{0}""", IO.Path.GetFileName(strFilename))
        header.AppendLine()
        header.AppendLine("Content-Type: application/octet-stream")
        header.AppendLine()
        Dim headerbytes() As Byte = System.Text.Encoding.UTF8.GetBytes(header.ToString)
        Dim endboundarybytes() As Byte = System.Text.Encoding.ASCII.GetBytes(vbNewLine & "--" & boundary & "--" & vbNewLine)
        headerbytelength = System.Text.Encoding.UTF8.GetBytes(header.ToString)
        endboundlength = System.Text.Encoding.ASCII.GetBytes(vbNewLine & "--" & boundary & "--" & vbNewLine)
        request.AllowAutoRedirect = True
        request.Timeout = -1
        request.KeepAlive = True
        request.AllowWriteStreamBuffering = False
        request.ContentType = "multipart/form-data; boundary=" & boundary
        'request.ContentLength = 0
        request.ContentLength = headerbytes.Length + New IO.FileInfo(strFilename).Length + endboundarybytes.Length

        Dim s As IO.Stream = request.GetRequestStream
        s.Write(headerbytes, 0, headerbytes.Length)
        Dim filebytes() As Byte = My.Computer.FileSystem.ReadAllBytes(strFilename)
        s.Write(filebytes, 0, filebytes.Length)
        s.Write(endboundarybytes, 0, endboundarybytes.Length)
        s.Close()

        response = CType(request.GetResponse(), HttpWebResponse)
        Dim receiveStream As Stream = response.GetResponseStream
        Dim readStream As New StreamReader(receiveStream, Encoding.UTF8)

        Dim jResults As JObject = JObject.Parse(readStream.ReadToEnd)
        Dim results As List(Of JToken) = jResults.Children().ToList()
        For Each item As JProperty In results
            item.CreateReader()
            If item.Name = "message" Then
                writer.WriteLine(item.Value.ToString)
            End If
            If item.Name = "status" Then
                writer.WriteLine(item.Value.ToString)
            End If
            If item.Name = "errors" Then
                Dim i As Integer = 0
                Dim spl() As String = Split(item.Value.ToString, "],")
                Do Until i > spl.Length - 1
                    writer.WriteLine(spl(i))
                    i = i + 1
                Loop
            End If
        Next

        If File.Exists(strFilename) Then
            File.Move(strFilename, (ConfigurationManager.AppSettings("HistPath") + createddate + "__" + e).ToString())
            writer.WriteLine("BLU File " + e + " was moved to: " + ConfigurationManager.AppSettings("HistPath"))
        End If

        response.Close()
        readStream.Close()

    Catch ex As Exception
        If ex.Message = "The remote server returned an error: (401) Unauthorized." Then
            writer.WriteLine("BLU File " + e + " is empty")
            If File.Exists(strFilename) Then
                File.Move(strFilename, (ConfigurationManager.AppSettings("HistPath") + e).ToString())
                writer.WriteLine("BLU File " + e + " was moved to: " + ConfigurationManager.AppSettings("HistPath"))
            End If
        Else
            writer.WriteLine(ex.ToString)
        End If
    End Try
    writer.WriteLine("------------------------------------------------END------------------------------------------------")
    writer.Close()
End Sub
Public Function AcceptAllCertifications(ByVal sender As Object, ByVal certification As System.Security.Cryptography.X509Certificates.X509Certificate, ByVal chain As System.Security.Cryptography.X509Certificates.X509Chain, ByVal sslPolicyErrors As System.Net.Security.SslPolicyErrors) As Boolean
    Return True
End Function

End Module

Answer 1

Maybe preemptive authentication is required. I'd recommend installing an app like fiddler if you do not know the parameters from a documentation.